They are angry that from 2013 S4C will be funded from part of the BBC licence fee rather than by the UK government.

It follows a demonstration outside the offices last Saturday when more than 300 people protested.

Bethan Williams, chair of Welsh language campaign group Cymdeithas yr Iaith Gymraeg, said: “It is obvious that the betrayal of the Government and the BBC has angered people in Wales.

“The cuts to S4C are unfair and threaten the future of our only Welsh language channel, but people are not willing to accept these plans for S4C. It is important that we act now and show that we are united.

“All the parties in the Assembly have asked culture secretary Jeremy Hunt to stop these plans and to hold a full review of S4C before coming to a decision. The British Government is ignoring the voice of the people of Wales by refusing this request, they have not considered the opinions of Welsh people from the start.”

The BBC insists it was the decision of the Government to make the corporation responsible for the channel.

A BBC spokesperson said: "The UK Government decided to reduce its funding for S4C as part of last October’s Comprehensive Spending Review, and Ministers considered a new partnership model with the BBC was the best way of securing the long term future of the service. This proposition was put to the BBC in the context of discussions on a new licence fee settlement.

"The BBC has made clear repeatedly that it has no ambitions to take over S4C. The Corporation is committed to an editorially independent S4C which attracts revenue from a range of sources, including the licence fee. Discussions between DCMS, BBC and S4C are ongoing."